Saka comes into the England team for Marcus Rashford, who drops to the bench despite his two goals in the 3-0 win against Wales.
Foden keeps his place in a front three alongside Saka and captain Harry Kane.
England will be without Raheem Sterling. The FA have said the Chelsea forward will miss the last-16 tie “as he is dealing with a family matter”.
An FA statement said: “Raheem Sterling is not available for selection for the Three Lions tonight as he is dealing with a family matter.”
Gareth Southgate has also kept faith with Jordan Henderson, who is preferred to Mason Mount in a midfield three alongside Declan Rice and Jude Bellingham.
Saka for Rashford is the only change from the team that beat Wales as Southgate sticks with a back four.
The Arsenal man scored twice in the 6-2 win against Iran but he struggled against the United States and was then an unused substitute in the 3-0 win over Wales.
But the 21-year-old is set to return to the team against Senegal.
England XI: Pickford; Walker, Stones, Maguire, Shaw; Rice, Henderson, Bellingham; Saka, Foden, Kane
Senegal XI: Mendy; Sabaly, Diallo, Koulibaly, Jakobs; Ciss, Mendy, Diatta; NDiaye, Dia, Sarr